Charged particles including electrons and ions are often encountered in the technical laboratory as well as in space endeavors and other natural environments. In the former instance, ionized particles are for example used in many semiconductor device-processing arrangements including impurity implantations, surface cleaning procedures and small object viewings. In the latter instance, charged particles often appear in vehicle extraterrestrial environments, in vehicle propulsion arrangements and in other plasma related situations including for example the Aurora Borealis phenomenon.
An energy analysis of the electron and ion particles found in these situations is often desirable in order to offset or accommodate the effects of charged particles on sensitive equipment encountering the particles. This analysis has heretofore been accomplished by sizable elements establishing particle controlling electrical fields capable of steering received particles into a predictable trajectory with electronic lens elements. A charged particle electrode assembly or lens assembly built around a plurality of machined analyzer electrodes disposed with the use of conventional hardware, e.g. fastener hardware passing through the electrodes, has been used in the past for such charged particle electrode assemblies or lens assemblies. In the lens assembly particles of a given energy are steered to different physical locations depending on the speed and direction with which they enter the device. The analyzer electrodes may be disposed in a variety of different patterns, patterns comprising either an energy high pass apparatus or an energy band pass apparatus. As suggested in this paragraph, an attempt is made herein to use the word xe2x80x9cassemblyxe2x80x9d in referring to charged particle energy analyzer electrodes or collections of these electrodes into a single charged particle energy analyzer and subsequently to use the word xe2x80x9carrayxe2x80x9d in referring to a plurality of charged particle energy analyzers joined together in a common group.
Energy analysis of charged particles is thus typically performed by some form of an electrostatic lens, hence the term electrostatic analyzer. Various arrangements of electrodes produce electric fields in such a device so that particles of a given energy are steered through the device. The number of possible electrode configurations used to accomplish this process is myriad; nonetheless each of these configurations falls into the categories of high-pass devices, in which charged particles of less than a given energy are rejected and only those with energy greater than a certain threshold are passed, and band-pass devices in which a narrow range of particle energies Is allowed to pass through the analyzer while particles with energies outside this range, both on the high and low ends of an energy range, are rejected. The present invention charged particle energy analyzer falls into the second category of devices and is regarded as a band-pass energy filter device.
The shapes of electrodes used in a charged particle energy analyzer can be simple (e.g. cylinders, spheres, etc.) or complex; such electrodes are usually machined from metal using conventional machining techniques such as milling or lathe turning. The machining techniques applied often limit the degree to which the size of these electrodes can be reduced, as do the size of the fasteners, such as machine screws, used to assemble the electrodes. Some devices, notably the planar retarding potential analyzer, employ fine metal screens to establish electrostatic potentials. Such screens can be made relatively fine using electro-chemical milling, at the expense of their being fragile. The charged particle energy analyzer of the present invention however is arranged so that it can be made quite small without sacrificing its ruggedness or its precision.
The present invention provides a charged particle electrostatic analyzer electrode assembly capable of low cost, accurate, repeatable micro-sized realization.
It is therefore an object of the present invention to provide a charged particle energy electrostatic analyzer that is small in physical size and capable of use in aircraft, spacecraft or other confined locations.
It Is another object of the invention to provide a charged particle electrostatic analyzer having internal electrodes of accurately controlled physical dimensions.
It is another object of the invention to provide a charged particle electrostatic analyzer electrode assembly that can be accurately reproduced in any desired quantity.
It is another object of the invention to provide a charged particle electrostatic analyzer electrode assembly that is compatible with fabrication using integrated circuit technology.
It is another object of the invention to provide a charged particle electrostatic analyzer electrode array comprising a plurality of charged particle energy analyzer electrode assemblies and capable of low-cost, accurate, repeatable micro-sized realization.
It is another object of the invention to provide a charged particle electrostatic analyzer of increased measurement accuracy capability by way of having precisely located and sized component electrodes.
It is another object of the invention to provide a charged particle electrostatic analyzer having a laminated internal electrode structure.
It is another object of the invention to provide a charged particle electrostatic analyzer electrode assembly comprised of layers of doped silicon semiconductor material.
It is another object of the invention to provide a charged particle electrostatic analyzer comprised of stacked etched through silicon semiconductor material layers.
It is another object of the invention to provide a miniaturized charged particle electrostatic analyzer in which electric fields within the analyzer steer charged particles of a selected energy range between input and output ports of the analyzer.
It is another object of the invention to provide a miniaturized charged particle electrostatic analyzer in which electrical potential applied to one or more analyzer electrodes is used to control the particle energy filtering characteristics of the analyzer.
It is another object of the invention to provide a charged particle energy analyzer that is improved in certain ways over the analyzers disclosed in my prior U.S. Pat. No. 5,506,413 and 5,541,409; each of these prior patents is however incorporated by reference herein.
It is another object of the invention to provide a charged particle electrostatic analyzer in which miniaturized particle steering electrodes are used to enable reduction of the charged analyzer electrodes to the 50-100 nanometer physical size range.
These and other objects of the invention will become apparent as the description of the representative embodiments proceeds.
These and other objects of the invention are achieved by miniaturized charged particle plasma analysis apparatus comprising the combination of:
a first conductive material electrode having circular apertures photolithographically disposed therein;
a second conductive material electrode having slot apertures, selectively aligned with said first conductive material electrode circular apertures, photolithographically disposed therein;
a third conductive material electrode having photolithographically disposed slot apertures, selectively aligned with said first conductive material electrode circular apertures and said second conductive material electrode slot apertures, located therein;
said first, second and third conductive material electrodes being assembled into a multiple electrode plasma analysis stack of physically isolated electrodes wherein said second conductive material electrode is also electrically isolated from a common interconnection of said first and third conductive material electrodes;
a source of selected electrical potential connected between said second conductive material electrode and said common interconnection of said first and third conductive material electrodes; and
a particle collection electrode member located adjacent said third conductive material electrode and connected via a current measuring element with a particle collection energy source.